| The modern society has higher and higher requirements for the quality of wireless communication,which makes the wireless communication system with a single function can no longer meet the requirements.Therefore,the intelligent antenna system with multi-function integration has been paid more and more attention by academia and industry recently.Among them,the reflector array antenna and transmitarray antenna based on space electromagnetic wave control array provide a good solution for the design of high-performance antenna array because of their strong electromagnetic wave controllability and low process complexity.In order to further increase the design freedom,the researchers propose a reconfigurable antenna array,and introduce the time dimension to increase the regulatory freedom of electromagnetic waves,which opens a window for the design of multi-function fusion antenna array,and has a very large application prospect.In this paper,three-dimensional frequency selection structure is used as the electromagnetic wave regulation unit,three reconfigurable implementation schemes are summarized,and three reconfigurable transmitarray antennas are designed to provide effective schemes for space-time modulation transmitarray antennas.Specific research is as follows:(1)From the perspective of array and element,the differences of reconfigurable transmitarray antenna and traditional transmitarray antenna in reconfigurable design are analyzed and compared,and three methods of reconfigurable phase shift for cell loading are given.In addition,after analyzing and calculating the load time ladder sequence of the reconfigurable transmitarray element,how the transmitarray antenna realizes the beam steering and multi-beam functions at harmonics.(2)Based on the three-dimensional frequency selection structure of the stacked slot line,the phase difference between the open-circuit coupling line and the short-circuit coupling line of the same electrical length is 180°,and two working states are realized;The odd-mode impedance and even-mode impedance of the slot structure are reasonably designed to ensure that the frequency response of the two states in the passband is the same,so that the 1-bit reconfigurable antenna unit is realized.On this basis,a reconfigurable transmitarray antenna is constructed.Simulation results show that the gain of the designed reconfigurable transmitarray can reach 21.5dBi and the 1dB gain bandwidth is 25%.(3)Two reconfigurable transmitarray units are designed based on the idea of current path switching: The first is the groove line-microstrip line-groove line,which is mainly by changing the working state of the PIN diode,so that the electromagnetic wave from the space coupling to the structure is transmitted in the current path with different electrical lengths.Through reasonable design of the length of the two paths,the phase difference of the transmitted wave at the center frequency is 180 ° under the two states.On this basis,the transmitarray antenna is further assembled,and its maximum gain is 21.8dBi and the 1dB gain bandwidth is 13.6%.In order to reduce the number of PIN diodes in the structure from four to two,the structure is improved,and the circuit is switched by controlling the slot lines in series.The results show that at the center frequency,the phase shift value of the transmitarray element differs by 178° and the insertion loss is lower than 0.1dB.The gain of the transmission array antenna can reach 21.9dBi,the gain bandwidth of 1dB is 16%,and the beam scanning can be realized by changing the phase distribution of the antenna in real time.Further using paraboloid technology,the in-band/out-of-band RCS reduction of transmitarray antenna can reach more than 10 dB. |
